CVE-2015-0239
Description
It was found that the Linux kernel KVM subsystem's sysenter instruction emulation was not sufficient. An unprivileged guest user could use this flaw to escalate their privileges by tricking the hypervisor to emulate a SYSENTER instruction in 16-bit mode, if the guest OS did not initialize the SYSENTER model-specific registers (MSRs). Note: Certified guest operating systems for Red Hat Enterprise Linux with KVM do initialize the SYSENTER MSRs and are thus not vulnerable to this issue when running on a KVM hypervisor.
Statement
This issue did not affect the kvm packages as shipped with Red Hat Enterprise Linux 5 as they lack support for sysenter instruction emulation.
This issue affects the Linux kernel packages as shipped with Red Hat Enterprise Linux 7. A future update may address this issue.
Please note that the Red Hat Enterprise Linux with KVM certified guest operating systems do initialize the SYSENTER MSRs and are thus not vulnerable to this issue when running on KVM hypervisor.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v2 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.2 | 4.4 | N/A |
| Attack Vector | Local | Local | N/A |
| Access Complexity | High | Medium | N/A |
| Authentication | None | None | N/A |
| Confidentiality Impact | Complete | Partial | N/A |
| Integrity Impact | Complete | Partial | N/A |
| Availability Impact | Complete | Partial | N/A |
Vector
Red Hat: AV:L/AC:H/Au:N/C:C/I:C/A:C
NVD: AV:L/AC:M/Au:N/C:P/I:P/A:P
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Varies by Context; Unexpected State; Alter Execution Logic
Acknowledgements
Red Hat would like to thank Nadav Amit for reporting this issue.
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